The present invention relates generally to efficiently downloading content data via a network, and more particularly to efficiently downloading multimedia content data via the Internet and displaying the data in a virtual three-dimensional space on a display device.
Today, users can, by using a browser program on a client personal computer (PC), download multimedia content data such as text, image and sound described in the HTML (Hyper Text Markup Language) and other languages from a Web server via a network such as the Internet to the PC, display it on a display device and produce sound via a speaker.
Various browser functions can be used for the download. For example, pieces of image data are downloaded to the client PC simultaneously or sequentially one by one in the order of occurrences of the HTML descriptions embedded in a particular previously displayed item of content. The image data can be downloaded in accordance with the progressive JPEG format or interlaced GIF format while concurrently displaying a temporary image in the process of being decompressed. It is possible to change images to be displayed by tracing links between a plurality of items of content, while thereby interrupting the downloading of the image data. By clicking on the display area in which a particular image is to be displayed, the order of capturing content data can be changed so as to capture the particular image data in the area earlier than others. In order to reduce the amount of image data to be downloaded, provisions can be adapted to first display a reduced image called a thumbnail, so that the original image to which the thumbnail linked is displayed by clicking on the thumbnail.
Recently, there has been development of three-dimensional Web browsers representative of three-dimensional Web content in a virtual three-dimensional space, and it is expected that a lot of three-dimensional Web content will be provided by Web servers over the Internet in the future. In viewing such three-dimensional content, a three-dimensional Web browser allows a user to zoom in and out an object representative of a given content image in a virtual three-dimensional space on a display, to thereby change his or her viewpoint relative to the object. The browser displays objects representative of images of all required items of content after having obtained such items of content.
Virtual three-dimensional display of content allows more content objects to be disposed in a virtual space than two-dimensional display of content by one dimension. Further, many virtual three-dimensional content objects are expressed with one or more polygons, and images are mapped as texture onto such objects. A lot of data is required to express a complex content object. Therefore, a user must wait for a long time before a lot of image data is downloaded over the network.
In the two-dimensional display of content, it is possible, when a particular item of Web content is displayed, to view another item of Web content by tracing links between items of Web content. A hyperlink indication is often embedded in Web content, and the user can be moved to another item of Web content by clicking on the hyperlink indication. The hyperlink has the advantage of permitting creation of an item of content to be linked to, independently of creation of an item of content to be linked from, so that an item of content at a physically distant location can be viewed through simple manipulation of the input device. In virtual three-dimensional display of content, however, the linking process by clicking on the hyperlink indication may be inconvenient.
A method has been developed for displaying objects representative of all hyperlinked items of content on the display based on the fact that a number of content objects can be disposed in virtual three-dimensional display of content. Such a method is disclosed, for example, by the inventors in Japanese Patent Publication JP 2000-172248 (A) published on Jun. 23, 2000, entitled “Electronic Information Display Method, Electronic Information Browsing Device and Electronic Information Browsing Program Storage Medium” (which corresponds to U.S. patent application Ser. No. 09/407,376 filed on Sep. 28, 1999). In the method and device, in accordance with the geometric relationship between a viewpoint of a user and an object representative of a subsequent item of content to be linked to, data of the subsequent item of content may be acquired.